Switching device



1941- E. c. MATTHEWS ETAL I 2,231,365

* v SWITCHING DEVICE I Filed May 10, 1938 2 Sheets-Sheet 1 FIG. Q rd I Q 25 FIG. 2 /5 f /5 HM HHM WWI HEW 4 a W 10 I3 L t-Zea EC. MATTHEWS A 7' TORNL'V 1941- E. c. MATTHEWS EIAL. 2,231,365

SWITCHING DEVICE Filed May 10, 1958 2 Sheets-Sheet 2 E. c. MATTHEWS ZF' G.A. PITCH/E ATTORNEY Patented Feb. 11, 1941 SWITCHING DEVICE Emil C. Matthews, Elizabeth, N. J., and George A. Ritchie, Brooklyn, N. Y., assignors to Bell Telephone Laboratories,

Incorporated, New

York, N.. 1., a corporation of New York Application May 10, 1938, Serial No. 207,056

6 Claims.

This invention relates to switching apparatus and more particularly to mechanically locking keys of the type used at telephone subscribers stations. Y Key structures of the type to which the present invention is particularly applicable are frequen'tly characterized as mechanically loekinl plunger type keys in that the depression of a button-capped plunger rod causes a lockins plate to move longitudinally against the action of a restoring spring until the top of a cone carried by the plunger passes below the lower surface of the locking plateafter which the latter returns to its initial position and holds the plunger in its depressed position. The longitudinal movement of the locking platedue to the subsequent operation of -another plunger disengages the plunger previously depressed. a1- lowing it to return to its normal position.

Structures of this nature which-are employed for switching purposes at subscribers stations are equipped also with'a non-locking key which usually serves as a hold" key, that is, it is actuated to hold a telephone line while some other switching function isperformed by thesubscribcr. Ilcrctofore, the actuation of a hold key or button caused the release of any previously actuated plunger during its downward travel so thatthe switching operation eiiected by the rcleaseof the previously actuated plunger took place immediately after-the switching operation performed by the hold button. Recently developed subscribers tation wiring plans require an appreciably longer time interval between the operation of the contacts controlled by the hold" button and the release of any previously operated line button.

It is therefore the object of this invention to delay the release of a mechanically locked contact controlling plunger for a relatively long period of time after the contacts controlled by the releasing medium have been actuated.

Thisobject is attained in accordance with a feature of the invention by causing the nonlocking key plunger to trip the plunger latching mechanism on its return movement rather than on itsdownward stroke as has heretofore been the custom. I

The invention will be readily understood from the following detailed description made with reference to the accompanying drawings in which: i

Fig. 1 is a front elevation of a key structure embodying the features of the invention;

Fig. 2 is a top plan view of the structure shown l inFig. l with part of the mounting plate broken away to expose certain structural details;

Fig. 3 is an end view of the structure shown in Fig. 1;

Fig. 4 is a section taken along the line 4-4 of Fig. 1 and looking in the direction of the arrows; v

Fig. 5 is a view illustrating a line plunger in locked position; I

Fig. 6 is a view illustrating the condition which prevails when the hold" plunger is partially depressed.

Fig. -7 is a view illustrating the condition which prevailsafter the hold plunger has been fully depressed and has completed a part of its re-; turn movement;

Fig. 8 is a top plan view of the mechanism which functions to introduce the desired time interval in the operation of the key;

Fig. 9 is a section taken along the line 9-9 of -Fig.-8 looking in the direction of the arrows, and

Figs. 10 and 11 are views, corresponding to Figs. 8 and 9, respectively, disclosing a modification oi the invention. I

A mountin plate ll of metal or other suitable material has secured to the under surface thereof equally spaced L-shaped brackets 42. Each bracket l2, secured to the mounting plate ill by means of screws I3 carries a spring pileup consisting of L-shaped spring elements ll and'insulating separators. The spring elements H are provided with integral tabs it: by virtue of which circuit connections to the key may be made.

, 'Below the mounting plate ill "and secured thereto by meansoi screws I6 is a second metal plate H. The spacing between the two plates [0 and i1 is effected by the sleeve-like members l8 which are tapped at either end to accommodate the screws I6. A slidable latch plate is slotted at each end and is adapted to travel between circular skirt-like projections on the sleeve-like members IS. The portion of each member lsbetween the integral extensions II is reduced in section to allow the slotted ends of the latch plate 20 to move freely. A restor-' ing spring 22 has one end secured to the stationary mounting plate It! and the other end to the slidable latch plate 20.

The key structure illustrated consists of a plurality of locking plungers and a single nonlocking plunger. Each plunger comprises a shank portion 25 on one end of which is secured,

'in any suitable manner, an insulating button pile-up. Substantially midway of the ends there is integrally formed on each of the locking plunger shanks a plunger locking cone 2!. The

plates in, 20 and I! are provided with circularapertures through which the assembled plunger extends. The apertures in the stationary plates i0 and I 1 are in alignment whereas the apertures in the latching plate 20 are, normally, slightly out of line with the apertures in the stationary plates Each of the plungers is provided with a metal collar 30 against which the insulating cap 2! is forced when placed on the plunger shank. A coil spring 3! encircles the upper portion of the cap or cone 2'! and is confined between the projecting portion of the collar 30 and the upper surface of plate I! so as to be compressed when the associated plunger is depressed.

The shank portion of the non-locking plunger, shown to the left of Fig. 1, is also provided with an integral cone-shaped projection 33 whose taper is inverted with respect to that of the locking cones 29.

The aperture in the latching plate 20 through which the non-locking plunger passes is extended to the left (Figs. 1 and 2) to provide a rectangular section, the extreme left limiting edge being chamiered as shown at 34. A shaft 35 extends across the rectangular section of the latching plate aperture and is freely supported in bearings effected by a perforation in each of the opposite sides of the latching plate. Rotatably mounted on the shaft 35 is a pawl 38. A sub stantially U-shaped resilient spring 31 is riveted to the latch-plate 20 in such a manner that the cross-bar of the U rests against one edge of the pawl 36 as clearly shown in Figs. 1, 5, 6, 7 and 9,

The key structure Just described operates in the following manner: when a button 28 of a locking plunger 25 is actuated or depressed, the metal cone 29, which forms part of the plunger rod associated with that button causes the locking plate 20 to move longitudinally against the action of spring 22 until the top of the cone 28 passes below the lower surface of the locking plate, after which the latter, under the influence of spring 22 returns to its initial position and holds the plunger in its depressed position. The longitudinal movement or displacement of the locking or latch plate 20 results from the camming action of the cone 29 on the periphery of the apertures in the plate. The longitudinal movement of the locking plate 20 due to the subsequent operation of another locking plunger releases the plunger previously depressed, allowing it to return to its normal position under the action of coil spring 3!. The last plunger depressed is locked in its actuated position in the manner already described. It will be observed at this time that the release of any locked plunger is effected during the downward travel of the subsequently actuated locking plunger.

In the case of the hold key shown to the extreme left of Figs. 1, 2, 5, 6, and '7, any locked plunger is released on the return movement of the hold plunger as will now be described.

Fig. 5 illustrates a locking plunger locked in its actuated position and the non-locking plunger in its normal position. In this position of the non-locking plunger, or hold" key, the lower right edge of the pawl 36 is in its normal position. As shown in Figs. 1 and 5 the pawl 33, in its normal position, is inclined at such an angle that its inner end extends between the collar 30 and the lower surface of the cone 33 with suitable clearances between the pawl and these members. That portion of the shank 25 immediately above the cone 33 is larger in diameter than the remaining portion so that the collar effected thereby serves as a stop to limit the upward movement of the plunger under the influence of spring 3!.

In Fig. 6 the non-locking plunger is shown partially depressed. As the plunger starts its downward movement, the upper right-hand edge of the pawl 36 is engaged by the under surface of the cone 33 and as the plunger continues its downward travel the pawl 36 is rotated on the shaft 35 against the restraining influence of the U-shaped spring 31. As the plunger continues its downward travel, the pawl 36 is cleared by the cone 33 just prior to the time when the plunger reaches the limit of its downward stroke so. that the pawl, under the influence of spring ll is returned to its normal position. The inner end of pawl 36 is then located above the cone 33 and, as illustrated in Fig. 7 which shows the non-locking plunger partially returned to normal under the influence of coil spring II, the tapered surface of the cone produces a camming action on the pawl 36 which is now restrained from rotating counter-clockwise by the latch plate surface 34. The pawl 36 and therefore, the latch plate 20 experiences a thrust to the left. As the non-locking plunger continues its return movement under the action of its coil spring 3i the latch plate 20 is displaced longitudinally to such an extent that the locked plunger, previously depressed, is now released and returns to normal under the action of its coil spring 3i. As this occurs, that is, as the latch plate moves a sumcient distance to permit the release of the locked plunger, the cone 33 rides off the pawl 33 and the upward travel of the plunger is arrested by the engagement of the collar on shank 25 with the under surface of the mounting plate Hi.

It is apparent from the foregoing description that the latching plate 20 experiences no longitudinal thrust when the non-locking plunger is depressed and it is not until some time after the plunger has reached its lowermost position and has started its return movement that the latching'plate is displaced longitudinally to release any of the plungers which have been previously actuated and locked in their actuated p0sitions. The contact springs controlled by the non-locking plunger are accordingly actuated and remain actuated for a short interval before those controlled by the non-locking plunger are returned to normal.

In the modification of the invention shown in Figs. 10 and 11 a. ratchet wheel or star wheel 50 is rotated on the down stroke of the "hold plunger and is held against rotation on the return stroke of the plunger by means of the dog or stop 5| so that the latch plate 20 is moved longitudinally on the return stroke of the plunger. The star wheel 50 is free to rotate on the shaft 54 which bridges the aperture 51 and is housed in the edges of the plate 20 which define the width of the aperture. The stop ii is similarly mounted on the shaft 53. A coil spring 52 has-one end secured to the latch plate 20 at 58 and the other end to the stop II at l3.

completed its travel over the straight portion of the tooth a and is situated below the level of the plate 20. Upon release of the hold button the tapered surface of the cone 33 engages the curved surface of the tooth c of the star wheel 50 and tends to rotate the star wheel in a counter-clockwise direction. The star wheel 50, however, is held against rotation by the pawl 5| so that, as the plunger returns to normal under the action of its associated coil spring i 3|, the star wheel experiences a lateral thrust due to the camming action of the cone 33. The latch plate accordingly is moved longitudinally to effect the release of any previously operated locking plunger. After the cone 33 rides oil the curved surface of the tooth c the latch plate is returned to its normal position under the action of spring 22.

What is claimed is:

1. In a switching device, a depressible contact operating plunger, latching means for locking said plunger in its depressed position, a second plunger and means for actuating said latching plate to release said first plunger, said means comprising a pawl pivotally mounted on said latching plate and a camming device associated with said second plunger. said pawl being rotated in one direction under the influence of said camming device during the downward stroke of said second plunger and moved longitudinally with said latching plate under the influence of said camming device during the return stroke of said second plunger.

2. In a switching device, a depressible contact operating plunger, a latching plate for locking said plunger in its depressed position, a pawl pivotally mounted on said latching plate and rotatable in one direction from its normal position, a second depressible contact operating plunger having a camming element which engages and rotates said pawl during the downward travel of said second plunger and means effective when said second plunger reaches its depressed position for returning said pawl to its normal position, in which position it is acted upon by the camming surface of said camming element during the return movement of said second plunger to cause said latch plate to operate and release said first plunger.

3. In a switching device, a plurality of contact operating plungers, means for locking said plungers in their operated positions comprising an apertured latching plate which is displaced longitudinally during the downward passage of said plungers through their respective latch plate apertures by a camming element associated with each of said plungers and restored to normal position by a restoring spring when the camming element is depressed beyond the level of the latching plate, a non-locking plunger having a camming element associated therewith and means for permitting the camming element of said non-locking plunger to pass freely through its corresponding aperture in said latching plate when said non-locking plunger is depressed, said means comprising a pawl pivotally mounted in the corresponding aperture of said latching plate and operatively associated with the camming element of said non-locking plunger.

4. In a switching device, a depressible contact operating plunger, a latching plate for locking said plunger in its depressed position, a second plunger and means for actuating said latching plate to release said first plunger, said means comprising a ratchet and dog combination carried by said latching plate and a camming device associated with said second plunger, said ratchet being free to rotate in one direction under the influence of said camming device during the downward movement of said secondplunger and which is held by said dog against rotation in the opposite direction and cooperates with said camming device during the return movement of said second plunger in causing the operation of said latching plate to release said first plunger.

5. A key switching unit including a depressible contact operating plunger, a second depressible contact operating plunger, a slidable latch plate having apertures through which each of said plungers may be depressed to a contact operating position, means integrally associated with said first plunger and cooperating with the edge of its respective latch plate aperture for causing said latch plate to be moved in a predetermined direction when the plunger is depressed, and other means for permitting the depression of said second plunger through its respective latch plate aperture without moving said latch plate, said means cooperating with said second plunger during its return movement to cause said latch plate to move in the predetermined direction.

6. In a switching device, a depressible contact operating plunger, a latching plate for locking said plunger in its depressed position, a second plunger and means for actuating said latching plate to release said first plunger, said means comprising a member pivotally mounted on said latching plate and a camming device associated with said second plunger, said pivotally mounted member being rotated in one direction under the influence of said camming device during the downward stroke of said second plunger and moved longitudinally with said latching plate under the influence of said camming device during the return stroke of said second plunger.

EMIL C. MATTHEWS. GEORGE A. RITCHIE. 

